JSON CRUD REST research
Work through https://www.w3schools.com/js/js_json_intro.asp you should understand REST CRUD.. and crucially if you have never uses a web api how you can create an application.
this article is a good overview https://technologyconversations.com/2014/08/12/rest-api-with-json/
The Web-sockets protocol is surmerised here: http://blog.teamtreehouse.com/an-introduction-to-websockets
A nice way to get your head around APIs is to practice with a well known one... https://www.w3schools.com/graphics/google_maps_intro.asp talks you through how to create web applications that use google maps API...
I'm not sure how they would assess this in an exam.... My guess would be they would give you a snippet of code and get you to explain it